Nunez started at third base, hit a two-run double and scored twice before he was removed for a pinch hitter in the fifth inning. The infielder, who was hit by a pitch on the left elbow earlier in the game, was shown on television shaking hands with teammates in the Giants' clubhouse.

The 30-year-old hit .308 in 76 games with San Francisco this season and has reached base safely in 40 of his last 42 games.

"A right-handed bat, a proven guy, hitting for a high average, he can play multiple positions," Red Sox manager John Farrell said from Seattle, where Boston lost 6-5 in 13 innings. "We'll work him in."

Nunez drove in 31 runs and had a team-high 17 stolen bases despite being slowed by a hamstring injury this month.

"He's very talented and that's why a lot of clubs wanted him," Bochy said. "He can run, he's a good hitter, he can play anywhere. I'm going to miss him because this guy was exciting. He's got a chance to get to the postseason so I'm happy for him. He'll help that ballclub."

Nunez did not rule out the possibility of re-signing with San Francisco in the offseason when he's scheduled to become a free agent. For now, Nunez said he's intent on helping the Red Sox maintain their lead in the AL East.

"I never listened really the last two week where I was going," Nunez said. "I just focused on playing. I don't read that much Twitter and those things. I am focused on who's pitching tonight, who's pitching the next day."

Boston general manager Dave Dombrowski said Nunez wouldn't report to the Red Sox until Friday.

"He's versatile for us, gives us another that we feel can help us give us some offense, which we do need at this time," Dombrowski said. "I think he'll play a lot for us. He's a good major league player."

The move could clear the way for the Giants to recall Pablo Sandoval from the minors, although Bochy said that's not likely to happen. The 2012 World Series MVP with the Giants, Sandoval signed a minor league contract with San Francisco last weekend after he was released by Boston, which signed him to a $95 million, five-year deal after the 2014 season.